Retentivity of RRAM Devices Based on Metal / YBCO Interfaces
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Retentivity of RRAM Devices Based on Metal / YBCO Interfaces A. Schulman1 and C. Acha1,2 1 Departamento de Física – FCEyN – Universidad de Buenos Aires, Pabellón I, Ciudad Universitaria, C1428EHA Buenos Aires, Argentina 2 IFIBA – CONICET ABSTRACT The retention time of the resistive state is a key parameter that characterizes the possible utilization of the RRAM devices as a non – volatile memory device. The understanding of the mechanism of the time relaxation process of the information state may be essential to improve their performances. In this study we examine RRAM devices based on metal / YBCO interfaces in order to comprehend the physics beneath the resistive switching phenomenon. Our experimental results show that after producing the switching of the resistance from a low to a high state, or vice versa, the resistance evolves to its previous state in a small but noticeable percentage. We have measured long relaxation effects on the resistance state of devices composed by metal (Au, Pt) / ceramic YBCO interfaces in the temperature range 77 K – 300 K. This time relaxation can be described by a stretched exponential law that is characterized by a power exponent n = 0.5, which is temperature independent, and by a relaxation time IJ that increases with increasing the temperature. These characteristics point out to a non-thermally assisted diffusion process that could be associated with oxygen (or vacancy) migration and that produces the growth of a conducting (or insulating) fractal structure. INTRODUCTION One of the crucial points for the development of information and communication technologies is the search of new memory devices. The Si-based devices are reaching limitations in information density, endurance and power consumption [1]. This is why a new paradigm is needed to store information in a reliably way. One of the possible candidates to overcome these technological challenges is the resistive memory devices (RRAM) based on the resistive switching (RS) mechanism, which have shown excellent properties in scalability, power consumption and operation speed, making them one of the more promising candidates to replace the actual flash memories [2-3]. One of the particular properties that must fulfill a non – volatile memory device is data retention. Here we propose to perform a detailed characterization of the lost of data retention by studying the time relaxation process after generating a switching in the remnant resistance state in YBa2Cu3O7–δ (YBCO) / metal (Au,Pt) interfaces in order to gain insight on the physical mechanism beneath the RS on these complex oxide devices.
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EXPERIMENT In this work, we sputtered different metals (Au,Pt) on the surface of an optimally-doped ceramic YBCO sample (Tc 90 K and Jc(77 K) 103 A/cm2) in order to investigate the time relaxation of the resistive states. The YBCO sample was prepared following the same procedures described elsewhere [4]. The sputtered electrodes, depicted in figure 1, have a width of 0.5 mm and a mean separation (6 + 2) mm. They cover the entire wid
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